The term 'illicit substance use' refers to a variety of substances that are either illegal to possess (e.g. heroin) or legally available, but used inappropriately (e.g. misuse of prescription medication, petrol sniffing). Substance use is a contributing factor to illness and disease, accident and injury, violence and crime, family and social disruption, and workplace problems. The use of inhalants (for example, petrol) can lead to serious health consequences, including brain damage, disability or even death (SCRGSP 2007a).

In the 2004-05 NATSIHS, information on substance use was collected from Indigenous people living in non-remote areas using a voluntary self-completion form. In 2004-05, 28% of Indigenous people aged 15 years and over who accepted the substance use form reported having used an illicit substance in the 12 months prior to interview, similar to the rate reported in the 2002 NATSISS (26%). Around half (49%) had reported having tried at least one illicit substance in their lifetime.

Substance use was more prevalent among Indigenous males than females. Half (54%) had tried an illicit substance (compared with 45% of females) and one-third (32%) had used at least one type of substance in the last 12 months (compared with 25% of females). Overall, recent substance use peaked among those aged 25-34 years (38%).

Marijuana was the most commonly reported illicit substance used by Indigenous people in 2004-05. Under half (43%) reported having tried marijuana and 23% had used it in the last 12 months. Amphetamines/speed was the next most frequently reported substance ever used (15%) or recently used (7%) by Indigenous people.

Along with alcohol, illicit substance use accounted for the greatest amount of burden of disease and injury among Australia's young people in 2003 (Begg et al 2007). This burden is often exacerbated when multiple substances are used in combination (AIHW 2007n). The 2004-05 NATSIHS showed that Indigenous young people aged 18-34 years who had recently used illicit substances were around twice as likely as those who had never used substances to regularly smoke (66% compared with 34%) and to binge drink on a weekly basis (28% compared with 13%). They were also less likely to report being in excellent or very good health (41% compared with 58%).

The 2004-05 NHS did not collect information on substance use among non-Indigenous Australians. However, results from the 2004 AIHW National Drug Strategy Household Survey showed that 15% of non-Indigenous people reported using illicit substances in the last 12 months - nearly half the rate reported by Indigenous Australians in the 2004-05 NATSIHS.